Spot Of Pepper Research Articles

The role of magnesium in plant disease

Magnesium (Mg), as an essential mineral element for plants and microbes, can have both indirect as well as direct effects on disease. Balanced nutrition is critical for the expression of disease resistance since nutrition is part of a delicately balanced interdependent system influenced by the plant’s genetics and the environment. A deficiency or excess of Mg can influence a wide range of physiologic functions because of these interrelated processes. There are fewer reports of direct effects of Mg deficiency or excess on plant disease than for many elements because of its participation in a wide spectrum of general physiological functions so that individual activities involved in defense, virulence, or pathogenesis are not as easily characterized. The ability of Mg to compliment or antagonize other minerals can result in different disease responses to Mg under varying environmental conditions. Fusarium wilt pathogens tend to be less severe when adequate Mg is available, and Mg increases resistance of tissues to degradation by some pectolytic enzymes of macerating or soft rotting pathogens. In contrast, high rates of Mg that interfere with Ca uptake may increase the incidence of diseases such as bacterial spot of tomato and pepper or peanut pod rot. The more general physiological benefits of Mg for active growth often obscure specific mechanisms involved in resistance to disease, although Mg is an important contributor to over-all plant health. A specific mechanism of defense to diseases enhanced by Mg includes increased resistance of tissues to degradation by pectolytic enzymes of bacterial soft rotting pathogens. Management of Mg nutrition to reduce disease, in balance with other minerals, is an underutilized tool for disease control.

Induced of Systemic Resistance against Gray Leaf Spot in Pepper by Enterobacter Species Isolated from Family Gramineae Plants in Dok-do

This study's aim is to isolate and characterize plant growth promoting Enterobacter species for the biological control of gray leaf spot in pepper. Screening was carried out from the rhizosphere of Agropyron tsukushiensi var. transiens (Hack.) Ohwi in Dok-do. Rhizobacterial isolates were partially identified by 16S rDNA sequencing and Enterobacter species were tested for plant growth promoting capabilities and the induction of systemic resistance in pepper against gray leaf spot caused by Stemphylium solani. Isolates were tested for production of indole-acetic acid and siderophore, and for phosphate solubilization. The application of isolates was effective in controlling gray leaf spot in pepper with E. asburiae (KNUC5007) and E. cancerogenes (KNUC5008 and KNUC5010) having the highest efficacy in reducing gray leaf spot severity. This is the first report of the biological control of gray leaf spot in pepper using rhizobacteria and it is hoped that this study will increase the utilization of Enterobacter species as plant growth promoters and biocontrol agents.

Morphological and molecular diversity of Colletotrichum spp. causing pepper spot and anthracnose of lychee (Litchi chinensis) in Australia

Since the 1980s a new disease has been affecting Australian lychee. Pepper spot appears as small, black superficial lesions on fruit, leaves, petioles and pedicels and is caused by Colletotrichum gloeosporioides, the same fungus that causes postharvest anthracnose of lychee fruit. The aim of this study was to determine if a new genotype of C. gloeosporioides is responsible for the pepper spot symptom. Morphological assessments, arbitrarily‐primed PCR (ap‐PCR) and DNA sequencing studies did not differentiate isolates of C. gloeosporioides from anthracnose and pepper spot lesions. The ap‐PCR identified 21 different genotypes of C. gloeosporioides, three of which were predominant. A specific genotype identified using ap‐PCR was associated with the production of the teleomorph in culture. Analysis of sequence data of ITS and β‐tubulin regions of representative isolates did not group the lychee isolates into a monophyletic clade; however, given the majority of the isolates were from one of three genotypes found using ap‐PCR, the possibility of a lychee specific group of C. gloeosporioides is discussed.

MultiLocus Sequence Analysis- and Amplified Fragment Length Polymorphism-based characterization of xanthomonads associated with bacterial spot of tomato and pepper and their relatedness to Xanthomonas species

MultiLocus Sequence Analysis (MLSA) and Amplified Fragment Length Polymorphism (AFLP) were used to measure the genetic relatedness of a comprehensive collection of xanthomonads pathogenic to solaneous hosts to Xanthomonas species. The MLSA scheme was based on partial sequences of four housekeeping genes (atpD, dnaK, efp and gyrB). Globally, MLSA data unambiguously identified strains causing bacterial spot of tomato and pepper at the species level and was consistent with AFLP data. Genetic distances derived from both techniques showed a close relatedness of (i) X. euvesicatoria, X. perforans and X. alfalfae and (ii) X. gardneri and X. cynarae. Maximum likelihood tree topologies derived from each gene portion and the concatenated data set for species in the X. campestris 16S rRNA core (i.e. the species cluster comprising all strains causing bacterial spot of tomato and pepper) were not congruent, consistent with the detection of several putative recombination events in our data sets by several recombination search algorithms. One recombinant region in atpD was identified in most strains of X. euvesicatoria including the type strain.

Price Discovery and Market Efficiency Revisited: Anecdotes from Indian Pepper Futures Markets

We have taken pepper as a commodity to explore the co-integrating vectors, nature/direction of causality, and subsequently, we try to model volatility spillover in Indian pepper futures and spot markets employing Johansen‟s co-integration, VECM, Granger causality and variance decomposition tests. We draw inferences from the study that unidirectional causality has been observed in case of pepper futures market. However, the adjustment of innovations or shocks in futures market is relatively faster than that of spot markets. For volatility modelling, we have employed models with their specifications, namely, EGARCH (2,2), EGARCH (3,3), MGARCH (Diagonal VECH and BEKK) for both pepper‟s spot and futures return-series. Study reveals that unidirectional spillover has been identified under EGARCH (2, 2) model and results obtained through EGARCH (3,3) model are not impressive. News impact curve depicts the steeper movement on the logarithmic conditional variance of futures and spot-return series, which is due to positive shocks rather than that of negative shocks. Conditional correlation seems to be dynamic in nature and the correlation between spot and futures returns of pepper has been witnessed the temporal changes.

Physiological disorders of Brassicas /Cole crops found in Swaziland: A review

Physiological disorders of Brassicas/Cole crops are abnormalities in leaf and stem morphology, colour, or both which are not caused by infectious diseases or insects. The abnormalities occur as a result of environmental stress, nutritional deficiencies or excesses on the plant. Reported causes of physiological disorders include genetic, environmental factors, nutrition, and cultural practices such as irrigation practices and tying leaves (blanching) for curd protection in cauliflower. Information was obtained through review of existing literature and informal surveys in the four agro-ecological zones of Swaziland coupled with brief interviews of key farmers and producers of Brassicas. Physiological disorders encountered in this study included premature bolting of Brassica juncea, head splitting in head forming Brassicas, failure of or multiple head formation called blindness, riciness in cauliflower, oedema, internal tip burn, black petiole, pepper spot, vein streaking necrosis and necrotic spot in cabbage. Measures to alleviate these physiological disorders of Brassicas are suggested. Key words: Physiological disorders, Brassicas/Cole crops, alleviating disorders, climate change.

A New Type of Strain of Xanthomonas euvesicatoria Causing Bacterial Spot of Tomato and Pepper in Grenada.

Bacterial spot of tomato and pepper (BSTP) can be caused by several Xanthomonas genospecies (2). BSTP is a major disease in Grenada where A and B phenotypic groups (Xanthomonas euvesicatoria and X. vesicatoria, respectively, [2]) have been reported (3). There is no previous report of group A strains, which are strongly amylolytic and pectolytic, in Grenada. In March 2007, tomato and pepper leaves with lesions typical of BSTP were collected in Saint David and Saint Andrew parishes of Grenada. Bacterial isolations were performed on KC semiselective agar medium (4), resulting in isolation of five yellow-pigmented, Xanthomonas-like strains. Three strains isolated from tomato or pepper in Saint David were negative for starch hydrolysis and pectate degradation, two tests that were found useful for strain identification in the 1990s (2). Two strains isolated from pepper in Saint David were strongly amylolytic and degraded pectate. Amplified fragment length polymorphism (AFLP) and multilocus sequence analysis (MLSA) assays targeting atpD, dnaK, efp, and gyrB were performed on the five strains from Grenada together with a type strain of each of X. euvesicatoria, X. perforans, X. gardneri, and X. vesicatoria as well as other reference strains of X. euvesicatoria and X. perforans as described previously (1). All strains from Grenada were identified as X. euvesicatoria regardless of the typing technique. On the basis of AFLP assays, the two strains with phenotypic features not reported in Grenada were closely related (distances of ≤0.002 nucleotide substitutions per site [1]) to a group of strains from India (ICMP 3381, LMG 907, LMG 908, and LMG 918). These two strains were also identical to the Indian strains based on MLSA, but differed from the X. euvesicatoria type strain by at least one nucleotide substitution in all loci examined. The three strains from Grenada that were negative for starch hydrolysis and pectate degradation had sequences identical to that of the type strain. Young leaves of tomato plants of cv. Marmande and pepper plants of cvs. Yolo Wonder and Aiguille were infiltrated (six inoculation sites per leaf, three replicate plants per cultivar per experiment, and the experiment was replicated once) using inoculum of each of the five strains from Grenada made from suspensions in Tris buffer containing approximately 1 × 105 CFU/ml. Two reference strains of X. euvesicatoria (NCPPB 2968 and LMG 922) were also inoculated as positive control treatments. Negative control treatments consisted of leaves infiltrated with sterile Tris buffer. Typical water-soaked lesions that developed into necrotic spots were observed 3 to 8 days after inoculation (dai) for all strains on all cultivars, except NCPPB 2968, which was not pathogenic on pepper cv. Aiguille. Xanthomonas population sizes from lesions plated onto KC agar medium (4) 25 dai ranged from 3 × 106 to 5 × 107, 8 × 107 to 2 × 108, and 9 × 106 to 2 × 108 CFU/lesion on tomato cv. Marmande and pepper cvs. Yolo Wonder and Aiguille, respectively. The epidemiological importance of this previously unreported group of X. euvesicatoria strains in Grenada needs to be assessed.

Genetic and Pathological Diversity Among Xanthomonas Strains Responsible for Bacterial Spot on Tomato and Pepper in the Southwest Indian Ocean Region.

Bacterial spot of tomato and pepper, a major problem in tropical climates, can be caused by several Xanthomonas genospecies. We examined the genetic and pathological diversity of a collection of 72 strains from the southwest Indian Ocean region as part of a regional research and development program to update inventories of agricultural pests and pathogens. Xanthomonas euvesicatoria, X. perforans, X. gardneri, and X. vesicatoria were identified in our strain collection. The identification of strains at the species level was consistently achieved by amplified fragment length polymorphism (AFLP) and multilocus sequence analysis (MLSA). Overall, X. euvesicatoria was the species recovered prevalently. MLSA data based on four housekeeping genes identified two to three sequence types per genospecies. It suggested that sequence variations primarily consisted of synonymous mutations, although a recombination event spanning several hundred nucleotides was detected for some strains of X. euvesicatoria on the atpD gene coding for the F1-F0-ATPase β subunit. The pathogenicity of strains was consistent with data found in the literature. Some pathological variations were primarily observed among strains identified as X. euvesicatoria. This study provides the first ever comprehensive description of the status of Xanthomonas species that cause bacterial spot of tomato and pepper in the southwest Indian Ocean region.

Pathogenic diversity of avocado and mango isolates ofColletotrichum gloeosporioidescausing anthracnose and pepper spot in Australia

Colletotrichum gloeosporioides is a major fungal pathogen of avocado and mango fruit in Australia and overseas. It causes anthracnose and stem-end rot in these crops but has also been identified as the causal pathogen of pepper spot of avocado and tear stain of mango. Research was initiated to determine the pathogenic diversity of pepper spot, with emphasis on avocado. Eighty C. gloeosporioides isolates obtained from avocado and mango fruit showing anthracnose and pepper spot symptoms were screened for pathogenicity, comparative aggressiveness and cross-infection potential by inoculating onto detached avocado and mango fruit, avocado leaf petioles and branches of young, grafted nursery trees, as well as avocado fruit and pedicels still attached to the tree. On detached, ripening avocado and mango fruit in the laboratory, it was found that pepper spot isolates were as capable as anthracnose isolates of causing anthracnose lesions. However, avocado isolates were significantly (P < 0.05) more aggressive than mango isolates on avocado fruit and mango isolates were significantly (P < 0.05) more aggressive than avocado isolates on mango fruit. In field inoculations, pepper spots were formed on developing avocado fruit and pedicels on the tree. Likewise, pepper spots developed on petioles and branches of nursery avocado trees, but not on their leaves. When all isolates were grouped according to symptom or host of origin, significant differences in lesion severity were demonstrated between isolates on avocado petioles in the glasshouse, with avocado pepper spot isolates being the most aggressive, followed by avocado anthracnose isolates then mango isolates from both anthracnose and pepper spot, respectively. On unripe avocado fruit in the field, the pattern was generally similar with the mango isolates being the least aggressive. There were more and less pathogenic strains present in the pathogen populations from both mango fruit and avocado fruit but neither were restricted to anthracnose or pepper spot groupings. Generally, a higher percentage of the most aggressive isolates was from avocado pepper spot. When isolates were grouped according to the orchard of origin, there were significant differences in aggressiveness to avocado both in the glasshouse and the field.

Reaction of the Core Collection of Peanut Germplasm to Sclerotinia Blight and Pepper Spot1

Abstract In 2001, entries from the peanut core collection, a subset of the USDA peanut germplasm collection, were planted in non-replicated plots in a field with a history of Sclerotinia blight caused by Sclerotinia minor. Variability existed among entries for reaction to Sclerotinia blight. Of the 744 entries evaluated, 11% had no disease, nearly 30% had &amp;lt;10% disease incidence, and only 21% had 50% disease incidence or more. Most of the resistant entries had an upright growth habit and were in early and mid-maturity groups. Many of the early maturing entries were susceptible to the foliar disease pepper spot which occurred throughout the study. Entries were selected for further evaluation in replicated plots based on a nil to low (&amp;lt;10%) incidence of Sclerotinia blight, adaptation and/or vigor, and other desirable characteristics such as an intermediate to prostrate growth habit and pepper spot resistance. Selected entries were retested in both 2002 and 2003 (n = 62) and compared to resistant (Tamspan 90), moderately resistant (Tamrun 96), and susceptible (Okrun) reference cultivars. Most entries (55 in 2001 and 46 in 2003) had disease incidence less than Tamrun 96 and similar to Tamspan 90. In 2003 when disease incidence was highest, all 46 entries with resistant reactions similar to that of Tamspan 90 had erect plant growth habits except for entries 208 and 582 which were prostrate, and entries 273, 128, and 804 which were intermediate. Resistance to Sclerotinia blight and yield similar to Tamspan 90, plant habit, and/or reactions to pepper spot and web blotch were used to select the best entries. Entries 208, 128, 804, 582, and 273 combined resistance to Sclerotinia blight, pepper spot, and web blotch with less than erect growth habits. Entry 103 had good Sclerotinia blight resistance and yield, but an upright growth habit. Entry 92 had an upright growth habit and low yield, but good Sclerotinia blight resistance. Entries 92 and 103 had upright growth habits but were among the best entries for resistant to pepper spot and web blotch. Entries 426, 184, and 562 were upright and susceptible to pepper spot, but had resistance to web blotch and the best resistance to Sclerotinia blight. These entries appear to be useful sources of resistance to Sclerotinia blight for breeding programs and for increasing the probability of finding additional sources of resistance in clusters of germplasm identified within the entire USDA collection.

DEVELOPMENT OF SPECIFIC PRIMERS FOR THE MOLECULAR DETECTION OF BACTERIAL SPOT OF PEPPER AND TOMATO

Bacterial spot of tomato and pepper is an important seed-borne disease caused by a diverse group of bacteria currently classified as four species of X. euvesicatoria (Xe), Xanthomonas vesicatoria (Xv), X. perforans (Xp) and Xanthomonas gardneri (Xg). The objective of this research was to develop PCR primer sets that allow the specific detection and/or identification of Xe, Xv, Xp and Xg strains, in particular in seed assays. AFLP® was used to identify markers specific for each of the four species. Marker fragments were sequenced and potential primer sets were evaluated in PCR for their specificity. For all species specific primers were obtained.

Host-Plant Resistance and Management of Bacterial Spot of Pepper

PP-255, a 3-page illustrated fact sheet by Ken Pernezny, Jeff Jones, Russell Nagata, and Nikol Havranek, describes the developments in the campaign to develop cultivars resistant to Xanthomonas euvesicatoria. Published by the UF Department of Plant Pathology, June 2008.

Comparison of two culture media for determination of the copper resistance of Xanthomonas strains and their usefulness for prediction of control with copper bactericides

Two bacteriological culture media were compared for determination of copper resistance among strains of Xanthomonas euvesicatoria and Xanthomonas perforans from pepper and tomato and Xanthomonas campestris pv. vitians from lettuce. Of 94 strains tested, 73 grew on glucose-nutrient agar (GNA) amended with 200 μg ml −1 of copper sulfate. None of the 94 strains grew on modified casitone-yeast extract (CYE) agar amended with copper. In vitro population studies supported the preliminary classification of strains as copper resistant. Reduction in populations of strains found to be resistant on GNA+Cu were less than one log unit after 2-h exposure to copper hydroxide suspensions in vitro. Addition of mancozeb to the copper hydroxide resulted in population reductions of 4–8 log units. Therefore, GNA+Cu is more appropriate for screening of Florida Xanthomonas strains for resistance to copper. Copper hydroxide alone, mancozeb alone, or a combination of these two compounds reduced bacterial spot of tomato and pepper significantly under low disease pressure. Reductions in disease ratings were as much as ten-fold in some experiments. Only the combination of copper and mancozeb was effective at higher disease levels.

Effect of different treatments to bacterial canker (Clavibacter michiganensis subsp. michiganensis), bacterial speck (Pseudomonas syringae pv. tomato) in tomato, and bacterial spot (Xanthomonas campestris pv. vesicatoria) in pepper

In ecological farming systems farmers can't use chemicals against pests. In ecological plant protection the aim is to prevent diseases; if it is not possible the use of allowed materials are permitted. Until now there haven't been enough effective and environmental friendly materials for seed treatment in organic farming. Seed borne diseases of tomato and pepper can cause serious losses in yield, so finding appropriate inhibitors has a great importance. Different materials were tested against these bacterial strains for seed treatment in this study. In vitro trials have shown that vinegar, cider vinegar, red wine vinegar and white wine vinegar have inhibiting effect against the causative agent of bacterial canker (Clavibacter michiganensis subsp. michiganensis), bacterial speck (Pseudomonas syringae pv. tomato) of tomato. These materials also have inhibiting impact on the causative agent of bacterial spot of pepper (Xanthomonas campestris pv. vesicatoria). Seed treatment with (natural alkaline material) sodium hydrogen carbonate (NaHCO3) had no effect on the examined bacterial strains. Among examined essential oils cinnamon oil seemed to be the most effective, but all oils decreased the germination ability. Thyme and savory teas were effective against Pseudomonas syringae pv. tomato. Other examined materials had insufficient bactericide impact (sucrose, NaCI, ethanol, valerian extract, peppermint tea). The germination test has shown that examined vinegar types don't decrease germination ability.

Pepper Spot ("Gomasho") on Napa Cabbage

HS-1101, a 5-page illustrated fact sheet by David Studstill, Eric Simonne, Jeff Brecht, and Phyllis Gilreath, describes this physiological problem affecting the midribs of Napa cabbage, the symptoms, possible internal causes and postharvest handling effects on pepper spot. Includes selected references and a table showing sensitivity by variety. Published by the UF Department of Horticultural Sciences, May 2007. HS1101/HS352: Pepper Spot ("Gomasho") on Napa Cabbage (ufl.edu)

Elaboração e validação de escala diagramática para a cercosporiose do pimentão

A cercosporiose do pimentão, causada pelo fungo Cercospora capsici, é uma importante doença que ocorre em condições tropicais. Devido à inexistência de métodos padronizados para quantificação desta doença em campo, uma escala diagramática com os níveis de 1,5; 3,5; 8,0; 16,5; 31,0 e 50% de área foliar lesionada foi elaborada e testada para a acurácia, a precisão e a reprodutibilidade das estimativas de severidade da cercosporiose do pimentão, sem e com a sua utilização. Na validação da escala diagramática, 50 folhas com diferentes níveis de severidade da doença, mensurados previamente com o programa AutoCAD®, foram avaliadas por 13 avaliadores, sem e com a utilização da escala diagramática. Foram realizadas duas avaliações com utilização da escala, com intervalo de sete dias, onde seqüências diferentes das mesmas folhas foram estimadas visualmente pelos mesmos avaliadores. A acurácia e a precisão de cada avaliador foi determinada por regressão linear simples, entre a severidade real e a estimada. Sem a escala, oito avaliadores superestimaram significativamente a severidade da doença. Com a escala, os avaliadores obtiveram melhores níveis de acurácia e precisão, embora quatro tendessem a superestimar a severidade, com os erros absolutos concentrando-se abaixo de 10%. Os avaliadores apresentaram boa repetibilidade e elevada reprodutibilidade das estimativas com a utilização da escala, o mesmo não sendo verificado sem a utilização desta. A escala diagramática proposta mostrou-se adequada para avaliação da severidade da cercosporiose do pimentão.

Incidence of Leptosphaerulina crassiasca in symptomless leaves of peanut in southern India

A Loculoascomycete fungus belonging to the genus Leptosphaerulina was found to survive as symptomless endophyte in the leaflets and rachis of peanut plant (TMV 7). Based on morphological and colony characteristics, it is identified as Leptosphaerulina crassiasca, a fungus that causes the pepper spot and leaf scorch diseases in peanut. Although several common endophytic fungi were recovered from the leaves of peanut, L . crassiasca showed a high relative density of infection. Owing to its endophytic nature, its pathogenicity could not be proved by infection studies. However, its identification as L. crassiasca suggests that this pathogen survives as symptomless endophyte in its host. There are limited studies on fungal endophytes of cultivated crops and hence, the present observation underlines the need to know more about the biology of endophytic fungi of crop plants.

CMS-Rf Genotype of Resistance Sources to Gray Leaf Spot in Pepper (Capsicum annuum L.)

A total of 19 selections derived from 4 sources of peppers with resistance to gray leaf spot (KC43, KC47, KC220, and KC319) were tested for their nuclear genotype of the gene conferring the ability to restore the cytoplasmic male sterility. All the selections derived from KC220 and KC319 were maintainers with a genotype of Nrfrf, while all the selections from KC43 and KC47were restorers with a genotype of N(S)RfRf.

Reduced genetic variation occurs among genes of the highly clonal plant pathogen Xanthomonas axonopodis pv. vesicatoria, including the effector gene avrBs2.

The bacterial plant pathogen Xanthomonas axonopodis pv. vesicatoria, also known as Xanthomonas campestris pv. vesicatoria group A, is the causal agent of bacterial spot in pepper and tomato. In order to test different models that may explain the coevolution of avrBs2 with its host plants, we sequenced avrBs2 and six chromosomal loci (total of 5.5 kb per strain) from a global sample of 55 X. axonopodis pv. vesicatoria strains collected from diseased peppers. We found an extreme lack of genetic variation among all X. axonopodis pv. vesicatoria genomic loci (average nucleotide diversity, pi = 9.1 x 10(-5)), including avrBs2. This lack of diversity is consistent with X. axonopodis pv. vesicatoria having undergone a recent population bottleneck and/or selective sweep followed by population expansion. Coalescent analysis determined that approximately 1.4 x 10(4) to 7.16 x 10(4) bacterial generations have passed since the most recent common ancestor (MRCA) of the current X. axonopodis pv. vesicatoria population. Assuming a range of 50 to 500 bacterial generations per year, only 28 to 1,432 years have passed since the MRCA. This time frame coincides with human intervention with the pathogen's host plants, from domestication to modern agricultural practices. Examination of 19 mutated (loss-of-function) avrBs2 alleles detected nine classes of mutations. All mutations affected protein coding, while no synonymous changes were found. The nature of at least one of the avrBs2 mutations suggests that it may be possible to observe one stage of an evolutionary arms race as X. axonopodis pv. vesicatoria responds to selection pressure to alter avrBs2 to escape host plant resistance.

Toxicity of mixed-oxidant electrolyzed oxidizing water to in vitro and leaf surface populations of vegetable bacterial pathogens and control of bacterial diseases in the greenhouse

Mixed-oxidant (MO) electrolyzed oxidizing (EO) water was generated by electrolysis of a 1.7% KCl (aq. w/v) brine solution. The MO EO water was a powerful bactericide in vitro at a dosage of mixed oxidants equivalent to 50 mg L −1 free available chlorine. Populations of Xanthomonas campestris pv. vitians, Pseudomonas syringae pv. coriandricola, and Erwinia carotovora subsp. carotovora were reduced from log 9 to log 10 CFU mL −1 to undetectable levels after 1 min exposure. Only E. carotovora subsp. carotovora was sensitive to a 5 mg L −1 dose of MO EO water. In greenhouse disease control experiments, 50 or 100 mg L −1 MO EO water failed to control bacterial leaf spot of lettuce, bacterial spot of tomato and pepper, or bacterial leaf spot of radish. A spray application of a copper hydroxide/mancozeb suspension was effective for control of bacterial leaf spot of lettuce and bacterial spot of tomato and pepper, reducing foliar disease levels up to 45%. Some phytotoxicity was observed at the 100 mg L −1 MO EO water dose. The lack of disease control on greenhouse plants with MO EO water may in large part be due to low mortality of the pathogen on leaf surfaces. In five of six experiments, no significant reductions in leaf surface populations were found for 50 mg L −1 MO EO water. In contrast, copper/mancozeb treatments reduced pathogen leaf surface populations by up to 5 log units when copper-sensitive strains were involved.